Characterization of the electrical properties of semimetallic Bi films by electrical field effect

The electrical field effect (EFE) was used to investigate and to characterize the electrical properties of Bi films. The samples were prepared in a capacitor configuration with Al as the gate electrode, Al₂O₃ as the dielectric and the thin (∼1300 Å) thermal-evaporation deposited Bi film sample serving as the other electrode. The dependence of EFE on the electrical field (up to electrical displacements ∼10⁷ V/cm or ≈10¹³[e]/cm² "surface" charge) and on temperature (15-300 K), and also the temperature dependence of Hall constant, were determined. The experimental results are shown to be consistent with the EFE theory of a semimetal film, assuming that: (1) the film has an interface "dead layer" (∼600 Å) that does not contribute markedly to EFE due to its extremely low carrier mobilities. Only in the rest, "good" part of the film, the electroconductivity is modulated and leads to a measurable EFE; (2) the temperature behavior of EFE follows the temperature dependence of the electron and hole mobilities and its sign is determined by their relative magnitudes.